A major problem in cancer chemotherapy is intrinsic or acquired drug resistance. We recently found, for the first time, that the loss or decreased expression of beta2- miocroglobulin (beta2M) is involved in the development of drug resistance. This is a completely novel drug resistance mechanism which has not been previously described in the literature. Therefore, the overall goals of this project are (1) to unravel the molecular and biochemical mechanisms by which beta2M causes drug resistance, and (2) to develop strategies to circumvent drug resistance due to the loss of decreased expression of beta2m. The Specific Aims are to (1) determine whether cellular levels of beta2m influence the cell cycle; (2) determine whether beta2m plays a role in apoptosis in drug sensitive cells, and whether its loss or decreased expression prevents apoptotic cell death; (3) modulate the expression of beta2m by cytokines and thereby circumvent drug resistance; and (4) investigate the regulation of beta2m expression in drug resistant cells, and determine the molecular mechanisms of beta2m gene suppression in these cells. In order to accomplish Specific Aim 1, experiments will be conducted to and decreases or increases cell proliferation, respectively, and (2) whether beta2m modulates the function of specific cell of specific cell-cycle, and decreases or increases cell proliferation, respectively, and (b) whether beta2m modulates the function of specific cell cycle-controlling proteins. To pursue Specific Aim 2, the role of beta2m in apoptosis will be explored by (a) evaluating levels in cells transfected with the beta2m gene in the sense or antisense orientation, and (b) examine whether anti-beta2m monoclonal antibodies in the absence or presence of chemotherapeutic agents, induce apoptosis in drug sensitive, but not in beta2m-deficient, cells. In order to accomplish Specific Aim 3, experiments will be conduced to evaluate the modulating effects of interferon-gamma (IFN- gamma) and tumor necrosis factor alpha (TNF-alpha), with or without doxorubican or vincristine, on beta2m expression in cells with reduced beta2m expression and in beta2m transfectants. In Specific Aim 4, we will determine whether (a) IFN-gamma or TNF-alpha induces specific transcription factors to enhance transcription of the beta2m gene in drug resistant cells, and (b) determine whether reduced expression of beta2m in resistant cells is due to decreased or absent positive regulatory transcription factors, or the presence of transcription suppressors. These studies will aid in understanding the molecular mechanism(s) of this novel drug resistance phenotype due to the loss or decreased expression of beta2m, and will be useful for the development of more effective chemotherapeutic or potential gene therapy strategies.